28 Jan
2011
28 Jan
'11
4:11 p.m.
On Fri, Jan 28, 2011 at 02:02:36PM +0100, Philipp Überbacher wrote:
rant_begin
Why can't log mean the same thing everywhere? Why does it need to be
base e here and base 10 there? Why is there no consistency?
And why is there no proper logarithmus dualis function? Because you
can simply do log(n)/log(2)? We've just seen how well this works.
How about:
log() - base 10
ln() - base e - logarithmus naturalis
ld() - base 2 - logarithmus dualis
rant_end
Libm has log(), log10, and log2().
The next obvious question is: Does the inaccuracy
reliably result in
values bigger than 11?
No.
If the input is a power of two, and you expect an integer as
a result, just do
k = (int)(log2(x) + 1e-6)
or
k = (int)(log(x)/log(2) + 1e-6)
or
int m, k;
for (k = 0, m = 1; m < x; k++, m <<= 1);
which will round up if x is not a power of 2.
Ciao,
--
FA
There are three of them, and Alleline.